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Thermoelectric Harvesting Using Warm-Blooded Animals in Wildlife Tracking Applications^{ †}

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## Abstract

**:**

## 1. Introduction

## 2. General Consideration for a Thermoelectric Energy Harvesting System Operated on an Animal

## 3. THC Design

## 4. Experimental Setup

**Table 1.**Relevant parameters that are used in the experimental set-up. For design parameters of the THCs see Figure 4.

Data of TEG (TEG-083-230-07, Thermalforce) | Data of Fur | |||
---|---|---|---|---|

Thermal Resistance ${R}_{TEG}$ | $(20\pm 1)$$\mathrm{K}$/$\mathrm{W}$ | Animal | Fur length | Fin length |

Thermal Conductivity ${\rho}_{TEG}$ | $595\times {10}^{-3}$$\mathrm{W}$/$\left(\mathrm{m}\mathrm{K}\right)$ | Merino sheep | 30–70 $\mathrm{m}$$\mathrm{m}$ | 10 $\mathrm{m}$$\mathrm{m}$ |

Seebeck-Coefficient $\alpha $ | 23.4 ± 0.4 mV/K | Domestic goat | 20–30 $\mathrm{m}$$\mathrm{m}$ | 3 $\mathrm{m}$$\mathrm{m}$ |

## 5. Experimental Results and Discussion

## 6. Summary and Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**Equivalent circuit model for a thermoelectric harvesting system attached to an animal. In typical scenarios, the thermal conductivity of the fur is significantly poorer than for the other samples.

**Figure 2.**Photograph of the five different versions of the thermal heat connector (THC), here for sheep’s wool, with variations in fin diameter and spacing. The fins height ${l}_{Fins}$ is 10 $\mathrm{m}$$\mathrm{m}$ for the experiment with the sheep wool and 3 $\mathrm{m}$$\mathrm{m}$ for the goat fur.

**Figure 3.**Left: Experimental set-up with the test device (THC and fur sample) put between two temperature-controlled plates. The THC with a fin length of 10 $\mathrm{m}$$\mathrm{m}$ was used with the short fur for demonstration purposes. Right: Schematic and equivalent circuit of the THC at the fur. The fins of the THC act as a parallel thermal resistance ${R}_{Fins}$ to the thermal resistance ${R}_{Fur}$ of the displaced fur. The remaining fur between THC and skin is represented as a thermal resistance ${R}_{Fur}$ in series.

**Figure 4.**Measured thermal resistances of the goat (red) and sheep (blue), together with the corresponding fin spacing (a) and front face (b) of the used thermal heat connectors together with their fin diameters.

**Figure 5.**$\Delta {T}_{TEG}$ at the TEG for the set of THCs as a function of the temperature gradient $\Delta {T}_{Total}$ between the animal’s fur and the environment. From the slope of the linear fits, the resulting thermal resistance of the THC can be calculated.

Fin ∅ | Spacing between Fins/mm | Total Front Face of Fins/mm${}^{2}$ | Weight of the THC/g | Resulting Resistance/K/W | Estimated Penetration Capability in the Fur | |||
---|---|---|---|---|---|---|---|---|

Sheep THC | Goat THC | Sheep THC | Goat THC | Sheep & Goat | ||||

Reference | - | 684 | 23 | 23 | 55 ± 1 | 25 ± 3 | - | |

5 mm | 3.7/2.3 | 168 | 17.4 | 12 | $46\pm 1$ | $30\pm 2$ | Fur not sliding aside but compressed | |

4 mm | 3.22.3 | 198 | 17.6 | 12 | $40\pm 1$ | $25\pm 2$ | Slides good | |

3 mm | 2.5 | 302 | $15,0$ | 11 | $76\pm 2$ | $38\pm 4$ | Ok, but get stuck due to small fin spacing | |

1.8 mm | 1.8 | 295 | 14.0 | 11 | $55\pm 2$ | $41\pm 3$ | Spacing too small for good penetration |

**Table 3.**Computed distance between fins and skin of the animal with Equation (2). The distance was calculated from the measured thermal resistance and a the theoretic value of ${k}_{Fur}$ and ${k}_{THC}$.

Fin ∅ | Sheep ${\mathit{d}}_{\mathit{Skin}}$/mm | Goat ${\mathit{d}}_{\mathit{Skin}}$/mm |
---|---|---|

Reference | 5.1 ± 2.0 | 2.2 ± 0.9 |

1.8 mm | 5.0 ± 2.0 | 3.8 ± 1.5 |

3 $\mathrm{m}$$\mathrm{m}$ | 7.0 ± 2.8 | 3.5 ± 1.1 |

4 $\mathrm{m}$$\mathrm{m}$ | 3.7 ± 1.5 | 2.3 ± 0.9 |

5 $\mathrm{m}$$\mathrm{m}$ | 4.2 ± 1.7 | 2.8 ± 1.1 |

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Bäumker, E.; Beck, P.; Woias, P. Thermoelectric Harvesting Using Warm-Blooded Animals in Wildlife Tracking Applications. *Energies* **2020**, *13*, 2769.
https://doi.org/10.3390/en13112769

**AMA Style**

Bäumker E, Beck P, Woias P. Thermoelectric Harvesting Using Warm-Blooded Animals in Wildlife Tracking Applications. *Energies*. 2020; 13(11):2769.
https://doi.org/10.3390/en13112769

**Chicago/Turabian Style**

Bäumker, Eiko, Pascal Beck, and Peter Woias. 2020. "Thermoelectric Harvesting Using Warm-Blooded Animals in Wildlife Tracking Applications" *Energies* 13, no. 11: 2769.
https://doi.org/10.3390/en13112769